Just got back from crippling a customer’s HP Pavilion computer after installing Windows XP Service Pack 3. I talked to HP and they know about this issue and is working on it.
If you install Service Pack 3 on an HP computer and your computer will not start follow these steps. When the computer reboots, you will get a black screen asking if you want to try to boot Windows normally (which will not work if you try) or in Safe Mode. It will say this has happened because of a recent hardware change/failure or software problem. Just use the arrow key to highlight any of the Safe Mode options, hit enter and wait for your computer to boot into safe mode. If you do not get this screen, hitting F8 while your computer is booting should do the trick. Once the computer starts in Safe Mode, (it will look different but it is ok) go to your Control Panel, Add Remove Programs, and finally click Windows XP Service pack 3 so that it uninstalls. Once you click it, it should ask if you want to uninstall but if not, highlight it and click the uninstall button at the top.